Microenergetic materials are energetic materials that are assembled in such a manner as to give structures with dimensions from tens to hundreds of micrometers. Integration of these energetic materials into microsystems in which the energy released (mechanical, thermal, chemical) through a reaction decomposition may be utilized is highly desired but has been elusive to achieve. Systems continue to be miniaturized, thus there is a strong desire to develop energetic materials with high efficiency in smaller volumes.
For materials in these types of microsystems, energy release (combustion, deflagration) characteristics at the mesoscale are critical. The term “mesoscale” is used to define a range of length scales that span from bulk, e.g., millimeter (mm) to centimeter (cm), to the molecular level, e.g., Angstrom (Å) to nanometer (nm). The success or failure of combusting an energetic material is linked to mesoscale phenomena. Such processes include conductive and convective combustion, radiation, and heat losses due to high surface area to volume ratios. Typically, success of materials in these applications is dependent, at least in part, on the rate of reaction propagation verses heat losses to the substrate. For example, most traditional monomolecular energetic materials, e.g., trinitrotoluene (TNT), cyclotrimethylene-trinitramine (RDX), High-Molecular-Weight RDX (HMX), etc., used in macroscale applications have failure diameters of at least a few millimeters and therefore are poor candidates for microenergetics. Therefore, it would be desirable to have a high total energy and fast reaction rate in a composite for use in microsystems.
Previous attempts at manufacturing explosives that use metal fuel, including compositions of Si (porous Si, or Si particles) in fuel/oxidant energetic mixtures have relied on metal fuel in a powder form that is affected by many other factors and influences. Moreover, the random nature of mixing particles lends to areas of aggregation of one material or the other, thereby diminishing effectiveness of the mix.
Material, energetic nanolaminates, that consist of alternating layers of metals that have exothermic heats of alloying have been described and are known. The resulting thin film structure is organized in 2-dimensions. The material is fabricated by sputtering mechanical roll-milling. However, successful attempts at incorporating such laminates into microenergetic materials have been elusive.
It would be desirable to have a metal fuel energetic composite that could have better overall rates of reaction, total energy output, and efficient manufacturability as compared to existing materials and methods of manufacturing.